1. Field of the Invention
The present invention relates to an electron emission display, and in particular, to a structure that transfers heat between a first substrate and a second substrate forming a vacuum envelope.
2. Description of Related Art
In general, electron emission elements can be classified into a first type using a hot cathode as an electron emission source, and a second type using a cold cathode as the electron emission source.
The second type of electron emission elements includes a field emission array (FEA) type, a surface-conduction emission (SCE) type, a metal-insulator-metal (MIM) type, and a metal-insulator-semiconductor (MIS) type.
An electron emission display includes electron emission elements arrayed on a first substrate and a light emission unit, including phosphor layers and an anode electrode, arrayed on a second substrate to thereby perform a light emission or image display (which may be predetermined).
During operation, the electron emission display radiates heat from the electron emission elements and the light emission unit. The electron emission elements radiate heat mainly due to emission from the electron emission regions, and the light emission unit radiates heat due to a high voltage continuously applied to the anode electrode and due to excitation of the phosphor layers. The heat radiated from the electron emission elements and the light emission unit is directly transferred to the first substrate and the second substrate, respectively.
Here, the amount of the heat radiation from the electron emission elements and the amount of the heat radiation from the light emission unit may be different, and therefore a difference in temperature between the first substrate and the second substrate is generated. In general, the temperature of the first substrate on which the electron emission elements are formed is higher than the temperature of the second substrate on which the light emission unit is formed.
Spacers arranged between the first substrate and the second substrate have a gradient in temperature along their height due to the difference in temperature between the first substrate and the second substrate. The gradient in temperature may cause the electric conductivity of the spacers to vary, thus causing scanning distortion of the electron beam.
In the case that electric conductivity of the spacers varies along the height of the spacers, distribution of the equipotential line around the spacers is deformed. Accordingly, when the electron beam proceeding from the electron emission elements to the light emission unit passes around the spacers, the electron beam deviates from its original trajectory, follows a distorted trajectory, and thereby fails to arrive at the target phosphor layers.
Therefore, with the conventional electron emission display, the quality of a realized image is decreased due to abnormal light emission of the phosphor layers.